border-1px($color)
  position: relative
  &:after
    display: block
    position: absolute
    left: 0
    bottom: 0
    width: 100%
    border-top: 1px solid $color
    content: ' '
    @media (-webkit-min-device-pixel-ratio: 1.5), (min-device-pixel-ratio: 1.5)
      -webkit-transform: scaleY(.7)
      transform: scaleY(.7)
    @media (-webkit-min-device-pixel-ratio: 2), (min-device-pixel-ratio: 2)
      -webkit-transform: scaleY(.5)
      transform: scaleY(.5)

border-1px-none()
  &:after
    display: none;

bg-image($url)
  background-image: url($url + "@2x.png")
  @media (-webkit-min-device-pixel-ratio: 3), (min-device-pixel-ratio: 3)
    background-image: url($url + "@3x.png")
